Bulletin of the American Physical Society
74th Annual Meeting of the Southeastern Section
Volume 52, Number 13
Thursday–Saturday, November 8–10, 2007; Nashville, Tennessee
Session MA: Nano, Materials and Biophysics at Oak Ridge National Laboratory |
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Chair: Ken Littrell, Oak Ridge National Laboratory Room: Scarritt-Bennett Center Laskey Great Hall |
Saturday, November 10, 2007 8:30AM - 9:00AM |
MA.00001: Opportunities in Inelastic Neutron Scattering at Oak Ridge National Laboratory Invited Speaker: The Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) are the two world class neutron scattering user facilities located at Oak Ridge National Laboratory. Inelastic scattering instruments designed to optimally utilize their source are either in, or will soon enter, the user program. The HFIR has three thermal and plans for two cold, neutron triple axis spectrometers in the user program. These instruments examine localized regions of {\bf Q} and $\omega$ space with tunable resolution. The spectrometers at the SNS cover broad ranges of {\bf Q} and $\omega$ space. The BASIS instrument, in the user program, uses near backscattering analyzer crystals to provide $3\mu$eV $\omega$ resolution. The ARCS thermal to epithermal neutron spectrometer is in commissioning and the Cold Neutron Chopper Spectrometer will enter commissioning soon. These instruments provide moderate, tunable resolution, and detector coverage out to $140^{\circ}$. The SEQUOIA spectrometer, complete in 2008, is the fine resolution complement of ARCS. The finest resolution is provided by the Spin-Echo spectrometer; complete in 2009. The HYSPEC spectrometer, available in $\approx$ 2011, will provide polarized capabilities and optimized flux for neutrons of thermal energies. Finally, the Vision chemical spectrometer will use crystal analyzers to access $\omega$ in the epithermal range. These instruments, along with representative science to be performed on each, will be presented. [Preview Abstract] |
Saturday, November 10, 2007 9:00AM - 9:30AM |
MA.00002: The Liquids Reflectometer at the SNS Invited Speaker: We have designed and constructed a horizontal-surface reflectometer as one of the first instruments at the Spallation Neutron Source. This instrument is designed to view liquid and solid surfaces in specular, off specular, near-surface small angle scattering, and crystalline diffraction geometries. The guide system supplies 2 {\AA} $<$ \textit{$\lambda$} $<$ 16.5 {\AA} neutrons at vertical incident angles ranging from 0$^{\circ}$ $<$ \textit{$\alpha$}$_{i} <$ 5.5$^{\circ}$ for free liquid surfaces and up to 45$^{\circ}$ for solid surfaces. Three bandwidth choppers, synchronized with the spallation source and operating at 15-60 Hz, provide neutrons in bandwidths ranging from 3.5-14 {\AA} at a fixed \textit{$\alpha$}$_{i}$ onto a sample. The sample stage enables all of the motions necessary for positioning liquid and solid surfaces, while the detector arm allows position-sensitive or pencil $^{3}$He detectors to view the sample at specular or off specular angles up to 90$^{\circ}$ and can scan out of the specular plane by up to 30$^{\circ}$. We will report on our progress commissioning the liquids reflectometer, which essentially involves making the vast parameter space accessible to the instrument accessible to expert and novice users in a coherent and reliable fashion. We have already served our first users and will present examples of data collected, demonstrate our data acquisition and analysis packages, and discuss instrument status. [Preview Abstract] |
Saturday, November 10, 2007 9:30AM - 10:00AM |
MA.00003: New High-Flux SANS Instrumentation at Oak Ridge National Laboratory Invited Speaker: A number of upgrades are in progress at the High Flux Isotope Reactor (HFIR), including the operation of a supercritical hydrogen moderator (T $\sim $ 20 K) that will be one of the ``brightest'' cold sources currently available. It will feed four cold neutron guides (CG1-4), each with new instrumentation. CG2 and CG3 are reserved for two new small-angle neutron scattering (SANS) instruments. A 40 m General Purpose SANS instrument that is funded by the Department of Energy (DOE) Office of Basic Energy Sciences is designed for CG2. The 35 m small-angle neutron scattering facility, Bio-SANS on CG3, is optimized for the study of biological systems and is the cornerstone of the Center for Structural Molecular Biology (CSMB), funded by the DOE Office of Biological and Environmental Research. The facilities are housed in a Guide Hall, along with a suite of other instruments, including a cold triple-axis spectrometer. Both SANS facilities will have variable wavelength and large area (1m$^{2})$ high count-rate detectors ($>$ 10$^{5}$ Hz) that can translate 45 cm off axis to increase the dynamic Q-range ($<$ 0.001-1 {\AA}$^{-1}$ overall). As the HFIR is one of only two reactors with a core flux greater than 10$^{15}$ neutrons/sec/cm$^{2}$, the beam intensities (up to 10$^{7}$/sec/cm$^{2})$ will be comparable to the best facilities worldwide. This will improve both the quantity and quality of data that we can collect from synthetic and biological macromolecules, allowing us to increase throughput, to use smaller sample volumes and to perform kinetic (time-resolved) experiments. \newline \newline In collaboration with V.S. Urban, W.T. Heller and D.A.A. Myles, Chemical Sciences Division, Oak Ridge National Laboratory; K.C. Littrell, Y. B. Melnichenko, K.M. Atchley, G.D. Wignall and G.S. Smith, Condensed Matter Sciences Division, Oak Ridge National Laboratory. [Preview Abstract] |
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